JPS5813680B2 - Tojirare Tabakku Water Kei Niokeru - Google Patents

Description

[Detailed description of the invention] Specification of Patent Application No. 25319 of 1972
1805 Publication) and Patent Application No. 103562 filed on September 10, 1979 (Japanese Unexamined Patent Publication No. 1977-64377)
As described in Prior to final drying of the sheet, the fibrous material fed to the process stream has a dryness substantially higher than the dryness of the wet sheet.

Depending on the density imparted to the fiberboard, the final drying takes place with simultaneous mechanical compression or without such compression.

For example, in the production of hard fibreboard, the wet sheet is subjected to very high mechanical pressures, so that before the final drying operation takes place, the compressed wet sheet is
% dryness.

In order to obtain this degree of dryness of the compressed sheet, the fibrous material discharged from the defibrator or crusher (hereinafter simply referred to as defibrator in this process) must have a degree of dryness of at least 50-55%. Must have.

Normal dryness must be maintained between 55 and 70% to allow a certain amount of water to enter the process without risking backwater to the drain.

When producing insulating fiberboards, the dryness of the wet sheet in this case is between 40 and 50%, while the sufficient dryness of the discharged fiber material is between 50 and 55%.

The use of water as a sealing agent in the section of the shaft passing through the defibrator must be limited or completely eliminated, for example by the use of steam.

Suitable fibrous materials for the fiberboard manufacturing process of the present invention include all types of lignocellulose-containing fibrous materials that have been disintegrated in a suitable manner, such as those in the form of sawdust whose chips are described below under the common name chips. wood, or straw;
Alternatively, it can be manufactured from bagasse or the like.

The disintegration operation would be carried out in an atmosphere of steam at atmospheric or elevated pressure up to 15 atmospheres overpressure, corresponding to a temperature range between 100 and 200<0>C.

When disintegrating conveniently well-heated wood chips in saturated steam, approximately 250 Kwh is usually consumed per ton of chips, calculated as bone dry material, if the disintegration operation is carried out between 160 and 170°C.

The increased consumption of energy at lower temperatures must be calculated.

The supplied electrical energy is almost quantitatively converted into thermal steam generation energy.

The heat products are concentrated in the grinding zone and sufficient water is necessary to avoid local overheating of the fibrous material, and the concentration of the material being processed in the grinding zone is inappropriate, i.e. more than 60% of the grinding material. .

The disintegration operation was carried out at 165°C and the chips had a dryness of 50% and a
℃, the concentration of the crushed material in the defibrator is about 47%, the chips are heated to 165℃ by steam, the defibration energy is 240Kwh per ton of bone dry material, and the chips are heated to 165℃ by steam. Assuming no dilution by incoming blockage water or humidity in the steam, the consistency of the pulp after delivery into atmospheric pressure is approximately 51%.

If the dryness of the chips is 55%, the density of the pulp under otherwise identical conditions is 54% of the ground material, respectively.
and the discharged pulp is 57.5%.

If the dryness of the chips is low, for example 45%, the concentration of the ground material and the discharged pulp is 42% each.
and 45.5%.

However, the dilution of the pulp usually occurs due to the inflow water and in reality must be calculated at a lower concentration than the pulp concentration.

The very high pulp density after passing through the defibrator, despite the addition of water partly as chip moisture and partly as condensed steam, is due to the generation of heat in the grinding zone, and this Therefore, a corresponding amount of water is evaporated as heat is generated.

When producing insulating fiberboards, the wet sheet before drying has a dryness of between 40 and 50%;
Chips with a degree of dryness of 50% can be disintegrated in the most preferred case.

According to the invention, the chips, if they have a very low degree of dryness before the disintegration step, are reduced to such an extent that the degree of dryness of the chips exceeds the degree of dryness that becomes apparent when starting the final drying of the board material. Some of the water is removed by mechanical compression.

For this purpose, the degree of dryness should be at least 50% and optimally 55%.
It must be increased to a range of ~70%.

However, at this high degree of dryness, the chips are at risk of harmful overheating or sticking in the grinding zone and of starting to burn. Backwater is arranged to be fed to the grinding material.

As an additional method to prevent the supplied backwater from being diluted by condensed steam in the defibrator, the backwater should be preheated to 100° C. or higher.

In this way, uniform evaporation of backwater can be obtained during the disintegration process, and the amount of backwater after pulp discharge is less than the amount of fed backwater.

However, it is difficult to indirectly preheat the backwater to a high temperature of 200° C., for example, due to scale, and in practical applications, preheating should not be performed above 170° C.

Water is easily removed when the chips are dehydrated by mechanical compression by utilizing the steam released when the pulp is discharged from the defibrator, which heats the chips sufficiently at 100°C and steams them. Therefore, this mechanical compression is related to the fact that a large volume can be obtained without increasing the compression pressure.

In order to increase the volumetric content of certain types of chips from 0.2 to 0.7, for example by compression, pressure must be applied to the uncooked chips, the size of which is 150
kg/crA, while for steamed chips a pressure of 70 kg/ctA is suitable.

Disintegration is carried out under pressure and the compressed chips are
Preheating of the chips can also save considerable amounts of green steam if fed directly into the defibrator at temperatures between 00°C.

At least half of the green steam supplied to the disintegrator can be saved in this way.

As an example, the following will be explained.

That is, if the chips after compression have a degree of dryness of 50% and a temperature of 100 °C when fed into a defibrator operated at a temperature of 165 °C, the discharged pulp will not pass through without additional water entering. It has a dryness of 57 to 58%.

If the dryness of the chips is 55% under otherwise identical conditions, the dryness of the pulp will be 64-65%.

Since such a concentration of ground material is obtained in the defibrator, the backwater according to the invention must be fed to adjust the concentration.

During the cooking of chips, variable amounts of steam are condensed on and in the chips, increasing their moisture content and thus increasing the importance of squeezing out the water.

If the chips have a dryness of, say, 50%, this dryness is reduced to 47-48% during cooking, and 410 kg of water, calculated as bone dry, is required per ton to obtain a dryness of, say, 55%. must be squeezed out of the chips, and this can actually be done if hot cooked chips are compressed.

Regarding the amount of liquid squeezed out in this way, 2. 5
0 kg is steam condensate and 160 kg is wood moisture.

Contrary to the above, for example, if the dryness of the chips is 50-60
% and then the chips are preheated with steam to 100 °C, if water is squeezed out of the chips before preheating, the chips will have a dryness of about 55%, and in the most favorable case results in a pulp with a final dryness of 64-65%.

In this case, the amount of moisture in the squeezed wood is about 330 Yu per ton of chips, calculated as bone dry without any amount of steam condensate.

It is advantageous in some cases to partially remove moisture from the wood before preheating the chips with steam, since the squeezed out water is firstly small and secondly free from impurities. This is because the content is low, making it ideal for reuse or rendering it harmless.

Removal of moisture before the preheating process is especially important when the process includes chip cleaning.

In such cases, in addition to the moisture inherent in the wood, a substantial amount of water accompanies the chips;
Values ranging between 350 kg are reached.

It is therefore appropriate to begin by centrifuging or compressing the chips in order to remove excess moisture before they are fed to the defibrator and are again preheated and compressed.

If very dry chips, for example with a degree of dryness of 55 to 65%, are treated by washing, only the adhering water has to be removed, which is carried out in the simplest manner by centrifugation.

Depending on the conditions existing in each individual case, the degree of dryness of the chips was variably adjusted to a suitable size between 50 and 70% and a chip temperature of 100° C. before feeding into the defibrator. can be done.

Excess water is then removed from the chips by centrifugation or compression before preheating the chips and feeding into the defibrator, or the water is removed from the chips partly before preheating and partly after. or by squeezing out after preheating before feeding into the defibrator or when feeding into the defibrator.

Of course, moisture can also be removed by pre-drying the chips with hot air, hot combustion gases or superheated steam.

It is more advantageous from a thermoeconomic point of view to dry the incoming chips than to dry the exiting bulb.

If cleaning of the chips is included in the process, the chips need to be freed of adhering water before undergoing the drying process.

If preheated chips are to be dried, such drying must be carried out with superheated steam so that the temperature of the chips can be maintained upon feeding into the defibrator.

Chips with a degree of dryness of 60% or more can be preheated directly with steam and fed into the defibrator.

However, it is usually more advantageous to adjust the dryness by compression after the preheating step, so that a dryness of 60% at a chip temperature of 100° C. is guaranteed.

If chips with the above dryness and temperature are disintegrated at 165°C, 200 kg of backwater at 130°C and 120 kg of sealed water at 65°C can be fed into the defibrator for every 1 ton of chips, thereby adding 67-6 if the backwater is ignored.
A final product with a dryness of 8% can be obtained by concentrating the ground material in a defibrator to about 55%.

It is important that the chips are sufficiently heated and cooked effectively, as this facilitates the dehydration or drying process.

Preheating of the chip is most simply carried out by directing steam directly through a moderately thick layer of the chip.

Here the steam has to overcome some counterpressure, which does not have to exceed several meters of water column.

If disintegration is carried out under pressure, the pulp is pumped through a cyclone to atmospheric pressure.

In this connection, if steam is used for preheating the chip, it must have a high pressure so as to overcome the resistance of the layers of the chip.

The cyclone can then be operated under low back pressure or a fan or compressor can be used to pump the steam through the layer of chips.

To explain the importance of high dryness of the pulp produced, it should be explained that when working with pulp with a dryness of 60%, approximately 300 kg of fresh material per ton of bone dry material water can be fed to the suspension without creating an excess of backwater.

If the pulp has a dryness of 65%, about 450 kg
of water can be added.

When chips are disintegrated in a steam atmosphere, some of the wood material is broken down by hydrolysis.

The amount of decomposed material is substantially temperature dependent and can be limited by carrying out the disintegration at a suitable temperature.

However, it is also possible to limit the decomposition by increasing the pH value of the ground material during disintegration, said disintegration
This is suitably done by adding a basic reactant, such as an oxide, hydroxide or carbonate of calcium, to the chips when they are fed into the defibrator.

The amount varies depending on the type of wood, but is usually as low as 1 to 2 kg of CaO per ton of ground material when calculated as bone dry matter.

In completely enclosed backwater systems, for example in the production of hard fiberboard, the concentration of decomposed wood material in the backwater is of the same order of magnitude as the decomposition calculated by the wood fraction.

It is therefore important to prevent the decomposition of organic matter as much as possible and in this way obtain a backwater with as low an amount of dissolved substances as possible.

At least some of the water that escapes when the chip is compressed is
It can be used for cleaning chips as spray water or sealing water in the board forming process, etc.

When manufacturing fiberboard by a wet process using a completely enclosed backwater system, this manufacturing process provides the following benefits:

1. Drying of the pulp after disintegration is unnecessary.

2. Drying of chips can be omitted.

3. The steam liberated during the pulp discharge removes the chips from 1
Effectively used for heating to 00°C.

4. Excess moisture in the chips is easily removed without adding additional heat.

5. If the defibrator is operated under pressure, the raw steam supplied to the defibrator can be substantially saved.

Savings of approximately 50% are often achieved.

6. Pulps with a dryness of up to 65-70% can be produced without the risk of overheating the fibers in the comminution zone.

In this respect, the dryness of the pulp is calculated independently of the fed backwater.

7. The use of steam or different types of fuel reduces investment and operating costs when compared to drying pulp or pulp.

The attached drawings schematically show the process schedule.

It is indicated to pre-treat the wood chips by dewatering them through a backwater circulation system and steaming followed by mechanical squeezing when feeding the wood chips to a defibrator.

The chips are guided on a conveyor 1 to a column 2 in which they are heated by steam which is also extracted by a cyclone 12 and fed to the column 2 via a pipe 3 by means of a fan 13.

The hot chips are passed through a grate 4 and a discharge device 5 to a guide device 6 which transfers the chips to a screw press 7.
The dryness of the chips is adjusted to an appropriate value by squeezing out moisture in this press 7, and then the chips are sent to the day five brator 8 via a preheater 35 and a screw conveyor 36. The reactor 8 is operated at a temperature of 165° C. and under a steam pressure of 7 atmospheres overpressure.

The water squeezed out as much as possible from the wood chips is discharged through the pipe 9 to the chip washing section.

The raw steam is supplied to the defibrator 8 through a pipe 10, and at the same time, a predetermined amount of backwater is supplied from a storage tank 19 to the defibrator 8 by a pump 20 and a pipe 22, and the backwater is first passes through a heat exchanger 21 and is heated to 130°C.

The pulp completely defibrated in the defibrator 8 is sent to a cyclone 12 through a duct 11, and the steam released from the cyclone 12 is guided to the column 2.

The pulp separated in the cyclone 12 is guided through a screw conveyor 14 and a hanging chute 15 to a pulp chest 16, which is simultaneously supplied with backwater from a storage tank 19 via a pipe 17 by a pump 18. .

The completed pulp suspension is transferred to a duct 24 by a pump 23.
The backwater discharged from the molding machine 25 is passed into the chest 26 and from there flows into the storage tank 19.

The wet sheet 27 is transferred to a high temperature press 28 and reduced by 50%.
The product 29 is mechanically dehydrated to a degree of dryness and finally dried by simultaneous application of combustion and pressure.

The squeezed out backwater is collected in a chest 30 and discharged into a tank 31, and from this tank 31 the backwater is passed through a pipe 33 by a pump 32 to a tank 19.
sent to.

Through the pipe 34, a limited amount of fresh or squeezed water is fed to the forming machine 25 as spray ice.

This invention can be implemented as follows.

(1) Moisture necessary to obtain the dryness is removed from the chips before the disintegration step by mechanically compressing the chips.

(2) 9 % by steam before the chips are fed to the crusher
Preheated to a temperature of 0-100°C.

(3) Mechanical compaction of the chips to adjust the moisture content of the chips is carried out when the chips are fed to the grinding device.

(4) The backwater supplied to the disintegrator is preheated to a temperature of 100 to 170°C in order to control the concentration of the suspension of pulverized material processed in the disintegrator.

(5) The steam liberated by disintegration carried out at atmospheric pressure is pumped through a layer of chips which is preheated by a fan or compressor.

(6) During disintegration carried out under steam pressure, the pulp and the steam are delivered under very high counterpressure, so that the freed steam resists the passage of the steam through the layer of chips to be preheated. You can overcome adverse pressure.

(7) At least a portion of the water escaping due to the mechanical compression of the chips is returned to the process, eg via chip washing or as spray water.

(8) Part of the moisture is removed before the chips are preheated, compressed and fed to the grinding device.

[Brief explanation of drawings]

The drawings are schematic diagrams showing each step of the fiberboard manufacturing method according to the present invention. 2: tower, 7: screw press, 8: disintegrator (defibrator), 12: cyclone, 16: pulp chess}, 19: storage tank, 25: molding machine, 27: sheet,
28: High temperature press.

Claims (1)

[Claims] 1. Disintegration of lignocellulose fiber-containing chips in a disintegration apparatus with a vapor phase of saturated steam at superatmospheric pressure and suspension of the disintegrated material discharged from said disintegration step in a backwater serving as a propellant liquid. forming a wet sheet with a pulp suspension; and squeezing water from the wet sheet by mechanical means and recycling the water as backwater to form a new pulp suspension. , and finally drying the sheet by evaporation of water. In a closed backwater system wet fiberboard manufacturing process, steam is released from the disintegrated material and the steam is used to dry the chips under atmospheric pressure. and then dewatering the steam-heated chips to at least 50% dryness, then feeding the thus heated and dehydrated chips to a disintegration step, and simultaneously with this step. A method for producing fiberboard by a wet method in a closed backwater system, characterized in that the backwater separated from the wet sheet is fed to a disintegration process to minimize overheating of the fiber material.